let add = (a,b)=>a+b;
let sub = (a,b)=>a-b;
let mul = (a,b)=>a*b;
let div = (a,b)=>{
    if(b != 0) return a/b;
    else return '除数不能为零！';
}

module.exports = {
    add, sub, mul, div
}
